Cycloparaffin production



1947- .w. E. ROSS ETAL CYCLOPARAFFIN PRODUCTION Filed July 17, 1944 mc uoLu mu mixtures.

Patented Jan. 194T 2,415,068 CYCLOPARAFFIN PRODUCTION UNITED STATES PATEINVTJJOFFICE" Company, Francisco, Calif., a corporation 1 of Delaware Application July 11, 1944, Serial No. 545,350

I M riam. (crate-ace) Resort to such procedures as the initial separation of a, fraction comprising both the methylcy clgpentanes and cyclohexane, subjection of thisfraction to isomerizing conditions effecting the conversion of methyloyclopentane to cyclohexano,

and fractionation of this isomerizate has been found unsatisfactory In addition to otherdifltimproved process for the more'efilcient production of cyclohexane from naphthenic gasolines and fractions thereof comprising methylcyclopentane and cyclohexane.

The cycloparaflins of hydroaromatic structure, particularly cyclohexane, are of great value as v starting materials and intermediates in the production of a wide varietyof organic products. A

culties, such a method generally does not enable the production of cyclohexane of any substantial degree of purity. Thus, the isomerizate will contain hydrocarbons such as the open chain paraflln hydrocarbons having seven carbon atoms to the molecule including, for example, 2,2-dimethylpentane and 2,4-dimethylpentane, the boilmost fertile source of these highly desirable materials resides in the naturally occurring hydrocarbon mixtures of naphthenic character such as naphthenic, natural and straight run gasolines,

etc. Other sources comprise hydrocarbon mixtures of naphthenic character, boiling in the gasollne boiling range obtained by fractionation of the products of many of the processes involvin the catalytic or thermal treatment of hydrocarbons or carbonaceous materials. As is well known. these readily available hydrocarbons constitute highly complex mixtures of a plurality of individual hydrocarbons, many of which have similar or closely approximating boiling points and many of which are capable of forming 'azeotropes with one another during distillation. Realizati n of the full advantages inherent in the many chemical processes relying upon the cycloparafllns of hydroaromatic structure as starting or intermediate materials has been handicapped by the lack of a process enabling eflicient production of the cycloparaflins of hydroaromatic structure on a practical scale from these available complex Not only is it imperative that such ing points of which are far too close to that of cyclohexane to enable separation by practical iractionating means. On the other hand, further separation of a methylcyclopentane concentrate and a higher boiling cyolohexane concentrate from this fraction and subjection of the v methylcyclopentane concentrate separately to cycloparaiilns of hydroaromatic structures be produced with-high yields, but it is essential that the product obtained be of a relatively high purity and yet involve the use of a minimum of opera tive steps. r

Efficient production of a cyc oparailln of hydroaromatic structure such as,-for example, cyclohexane from a readily available hydrocarbon mixture of naphthenlc character involves not only the problem of recovering substantially all bf the cyclohexane inherently present insuch mixtures, but the simultaneous conversion of the cycloparafiins of non-hydroaromatic structure such as methylcyclopentane to cyclohexane. Separation of either or both of these. cycloparafnns from the complex hydrocarbon mixtures in which they are generally encountered by such methods as fractional distillation, if at all possible, is often rendered so involved and delicate an operation as to render it highly impractical.

isomerizin'g conditions will result not only in the loss of methylcyclopentane in the cyclohexane concentrate, but will still present the difllculty of separating cyclohexane'from admixture with C1 open chain paramns in the cyclohexane boiling range. By the term hydroaromatic cycloparamns," as used throughout this specification and appended claims is meant the cycloparafllns having a hexamethylene ring such as, for example, cyclohexane and the alkyl cyclohexanes, to distinguish them from cycloparamns of non-hydroaromatic structure comprising those having pentamethylene rings such as, for example, methylcyclopentane and other alkyl cyclopentanes.

It is an object of the present invention to provide an improved process for the more emcient production of cycloparamns of hydroaromatic structure from hydrocarbon mixtures of relatively wide boiling range such asnaphthenic gasolines or fractions thereof comprising cycloparafhns of hydroaromatic and non-hydroaromatic structure in admixture with open chain paraflin hydrocarbons of substantiallythe same boiling range.

Another object of the invention is the provision of an improved process for the more efllcient production of cyclohexane from hydrocarbon mixtures of relatively wide boiling range such as naphthenic gasolines.

Stih another object of the invention is to Provide an improved process for the more efficient production of cyclohexane from naphthenic gasoline fractions comprising methylcyclopentane and cyclohexane in admixturewith open chain paraflinic hydrocarbons inseparable therefrom by fractionation. Other objects and advantages of the invention will become-apparent from the following description thereof.

In accordance with the proccss oi the invention cracking zone.

merizlng conditions to eflect the conversion oi 'cycloparamns of non-hydroaromatic structure to cycloparafllns of hydroaromatic structure.

The fraction comprising cycloparamns of hydroaromatlc structure separated from the charge will unavoidably comprise some methylcyclopentane I and open chain paramns particularly branched chain heptanes inseparable from cyclohexane by such means as fractionation on a practical scale. The fraction comprising cyclopentane and a fraction comprising cyclohexane. The fraction comprising methylcyclopentane will generally boil in the range of from about 65 C. to about75 C. and will generally comprise some normal hexane and a small amount of benzene. The cyclohexane fraction will generally boil within the range of from about 75 C. to about 85 C. and will comprise beside the cyclohexane methylpentanes and some methylcyclopentane. Al-

though it is preferred to select as the fraction passed into fractionator 4 a fraction boiling in the range of from about 65 C. to about 85 C. a fraction of somewhat wider boiling range may suitably be used. Under such conditions at least hexane in admixture with open chain parafllns is I subjected to thermal cracking conditions controlled to eilect the substantially selective cracking of the open chain paraflln content of the mixture to lower boiling hydrocarbons readily separable from' the cycloparaiiins. The resulting cracked products are fractionated to separate therefrom cyclohexane of high purity free of any substantial amount of open chain paraflins and a fraction consisting essentially of the methylcyclopentanes originally present in the charge to the The fraction comprising the methylcyclopentane is recycled to the isomerization zone. As will be apparent from the following detailed description thereof, the invention not only provides for the production of cycloparaflins of hydroaromatic structure from natural gasolines with substantially improved efllciency on a practical scale, but enables the obtaining of the desired product on a large scale in a greater state of purity.

In order to set forth more fully the nature oi the invention it will be described herein in detail in its application to the production of cyclohexane from hydrocarbon mixtures of naphthenic character in the gasoline boiling range, with reference to the attached drawing in which the single figure represents a more or less diagrammatic elevational view of one form of apparatus suitable for executing the process of the invention.

A hydrocarbon mixture of naphthenic character such as, for example, a n'aphthentic straight run gasoline is forced through valved line I into a feed fractionator 2. Within feed fractionator 2 a fraction comprising mcthylcyclopentane and cyclohexane is separated and forced through A valved line 3 into a'second fractionator 4. A

part of the material lighter boiling than methylcyclopentane may be eliminated overhead in fractionator 4, and hydrocarbons higher boiling than cyclohexane are eliminated as bottoms.

The methylcyclopentane fraction separated within fractlonator 4 is forced through line 1 into a methylcyclopentane conversion zone 8.

Within conversion zone 8 the methylcyclopentane fraction is contacted under cycloparafiln isomerizing conditions with an isomerization catalyst. Suitable catalysts comprise those containing a metal halide of the Friedel-Crafts type, particularly those comprising a halide of aluminum such as AlCl: and/or AlBrs. Particularly suitable catalysts comprise the organo-aluminum halide complexes, preferably a preformed aluminum chloride hydrocarbon complex. Other suitable catalysts comprise, those of the molten salt type containing the aluminum halide in admixture with one or more halide salts. The temperature in conversion zone 8 is maintained in the range of from about 20" C. to about 100 C. and preferably from about C. to about 90 C. The particular temperature chosen within this specifled temperature range will be governed to at least a substantial degree by the particular catalyst employed. When utilizing a preformed aluminum halide hydrocarbon complex as the catalyst a temperature in the range of from about C. to about C. is somewhat preferred. A hydrogen halide promoter such as, for example, hydrogen chloride is introduced into the conversion zone by means of line 9. The hydrogen chloride is added in an amount equal to from about 0.1 to about 3% and preferably from about 0.5 to

' about 2% by weight of the hydrocarbon charge naphthenic gasoline fraction comprising methyl- I cyclopentane and cyclohexane from any other source may be separately introduced through valved line B into line I and may comprise a part or all of the charge to the system.- The fraction passed into fractionator 4 is of sufficiently wide boiling range to comprise substantially all of the methylcyclopentane and cyclohexane originally present in the straight run gasoline. A fraction boiling in the range of from 'about 65 C. to about 85 C. has been found particularly desirable. Such a fraction will unavoidably comprise a number of other hydrocarbons besides methyloyclopentane and cyclohexane, particularly normal hexane and straight and branched chain heptanes and some benzene. Within fractlonator 4 the hydrocarbon fraction is further fractionated to separate a fraction comprising methylcycloto the conversion zone. Higher or lower concentrations of the hydrogen chloride may at times be desirable depending upon variation in operat-' ing conditions. Under these conditions methylcyclopentane will be converted to cyclohexane in conversion zone 8.

Eiliuence from conversion zone I is passed .through line I I into a stripping zone l2 wherein a vapor fraction comprising the hydrogen chloride promoter is separated and recycled to the conversion zone 8 by means of line 9. Make-up hydrogen chloride is introduced into the system by means of valved line II. Liquid lnrdrocarbons are passed mm the strlpper'lZ and forced through line l4 into a product separating zone represented in the drawing by the single fractlonator l5. Within fractionator l6 materiallower boiling than cyclohexane and comprising unconverted methylcyclopentane is separated as a vapor fraction and recycled at least in part through lines l1 and I8 to the conversion zone. The stream thus recycled may be subjected to a fractionation to effect separation of hydrocarbons other than methylcyclopentane therefrom prior to passage to'the conversion zone. Cyclohexane of a purity of or better is separated as an intermediate product in through valvedline ll.

: in a straight run naphthenic converted to cyclohexane under theaecouditions is illustrated by i irom 65 C. to e traction is given in Table IincolunimL, This A fraction was then subjected tog-iurther fractionspurity of 96% was obtained v composition thereoi shown in columeE of Table I.

amount oiopen iractionator ll and removedthereirom through valved line It as a dual product Material-higher boiling than cyciohexan'e comprising some bicyclic compound formed during the isomerization operation is separated from column ll as-bottoms The emciency with the iollowing example.

Erma! naphthenic gasoline was trac- A straight run V tionated to separate therefrom a methylcyclopentane-cyclohexane iraction boiling in the range or 85' C. The composition this tion to separate therefrom a concentrate having a boilingrange o! from; 65'

C. to '15 O. and a cyclohexane concentrate nav ing a boiling" rangeot from compositicnoithemethylcyclopentane and hexane concentratession zone. A conversion or methylcyclopentane of equilibrium was obtained. They-composition oi the isomerizateia given in column!) of Table I. By further iractionation or the isomerizate a cyclohexanefoi a which methylcyclopentane gasoline Iractionis as indicated by the positioned in a '75, O to 85" C.,: The yclois'given in Table I inwcollumns B and .Cresbectively. The, meumcyao.

halide hydrocarbon complex,

eliminated overhead through valved M an 1.

hexane,

l D B A B O, m -(lyclohexx u ,ane

product Boiling range, 0...... so-as 615- 75-86 Composition, percent i A i by volume: r x i Methylpentancs. 2.5 8 19 n-Hexane 36 25 fiin'i'e th .lperlitansu 3, 14 B Y y 0P I tane 37 48 l 12 "Cyolobexana 1L5 -84. 84 00 Benwne 7 8 l 8 I Undetermined- 2 2 The cyciohexane oi high purity thus produced represents the greater. pentane contentoriginally presentin the iced. It does. however not comprise the cyclohexane originally present in within iractionator 4. Thepcyclohexane concen comprise, beside the cyclohexane. a substantial in accordance with the process or the invention hexane and methylcyclopentane comprised in the part or the methylcyclochain heptanes, certain isomers 1 or which cannot be separated from the cyciohexaneby such means as iractionation on a practical However.

. section of the cracking: 1' introduced in the final substantially all of the c cles? cyclohexane fraction is ultimately recovered as cyclohexane of a purity 01 at least or better.

. In accordance with the process of the invention tractionator l is passed thermal cracking zone 25. The thermal cracking zone may comprise any suitable such as, for example, an externally heated coll type oi apparatus 70 .the cyclohexane concentrate separated within through line Ilto a rurnace structure and optionally iollowed by a zone of enlarged cross sectional area such as a reaction chamber. Prior to passage of the cyclohexane concentrate into the thermalcracklng zone it is preferably subjected to atreatment to eifect the removal oi aromatic hydrocarbonsthereirom by means not shown iri the drawing. Thuslthe benzene contained in the 'cyclohexane concentrate flowing throughwline 10 24 may be removed hereirom by such means as treatment with suliuric acid or a selectivesolvent for, hydrocarbons. Within conversion zone Ilthecyclohexane concentrate is subjected to an elevated temperature in the range of from about SOO'QC. to about C. and preierably Iran-about 550'0. to about 850' C. for" a oi tlme"ranging from about 5- to about 80 secones and preierablytrom about 10 to about so methylcyclopentane seconds." A'pressure phone to not su have been round however, be employed Under these conditions in the range or from atmosslightly elevated pressures for exampl a iractionating zone represented inxthe drawing by the single iractionator I2.

Within fractions-tor :2 material lower boiling than cyclohexane and comprising the methylcyclopentane originally present in the chargeto the cracking zone is separated overhead through line a and recycled at least in part through lines to. the isomerization zone 8. Cyclocomprising a substantially reduced dimethylpentane content is taken as an intermediate product from fractionator I! through valved linegli. Material higher boiling than cyclohexaneis eliminated as albottom product from iractionator 32 by means The material thus eliminated as bottoms through line 36 may be recycled in part to an intermediate zone and is preferably men or the cracking zone to dilute the hydrocarbon stream flowing ac ta n e w" enabling more eiiicient lectivity of cracking. from the crackinscitheopen for example, of olennic structure. The

control, therein, and

- jcyjcloheaane taken oil'- through 'valvedline; as -(optionally the entireeiiiuenceoi 2!) ispreierably subjected suitable olefin removal treatment comprising, for example. sembbingwith a selectlve-solventior acid such as sulfuricacidtby means notshown in the drawi of unsaturated hydroin; to assure the removal carbons therefrom- Apart or all of the ttom productin iractionator ll may be passed from line 2| through line 8| to the inlet of cracking zone 25. The separation of open chain paramna from admixed cycloparai'iins,inseparab1y.by fractiona- "tially-in excess oi about 500 pounds suitable. Higherpressures may.

open chain paramns admixedwith the cyclcfor example, hydroof valved line 36.

the feed not the". a ;therethrough, thereby increasing rate of now,

amount or methylcyciopentane unavoidably commaterial eliminated as a cyclopentane and cyclohexane tion mea'na'is Burnt: II A cyelohexane concentrate containing'188% by volume oi cyclohexanc and 7% by weight or dimethylpentanes was subjected to selectiv a contact time of from 9 to 12 seconds. 43% f hydrocarbon mixtures in accordance with the invention over methods involving the isomerization of a single fraction comprising both methylin the charge.

Exmu III a portion of the methylcyclopentane-cycloonnnally P e nt oi the dimeth'ylpentane present in the charge to hexan fraction boiling in the range or from 65 C. to 85 C. separated (tom the naphthenic gasoline charge in Example I. the composition of which is given in column A of Table I, was

isomerized by contact with a preformed immi-- hum chloride hydrocarbon complex at a temperature of 80 C. with a contact time of 26 minutes. Hydrogen chloride in an amount equal to 1% by weight of the charge was added. The

isomerisate had the following composition:

Methylpentanes 18 Normal hexane -4.-- 20 Dimethylpentane 3 Methylc yclopentane 16 Cyclohexane 40 Benzene- -7 Higher boiling material.

The isomerizate was distilled to eflect the separation of cyclohexane therefrom. The cyclohexane cut thus produced contained only 811% by volume of cyclohexane. The rest oi the hexane cut consisted or benzene, 5%, and dimethylpentanc. 7%.

the parafllnic content of such atraction on a A large scale would be so costly as to render the process economically unfeasible. The process oi the invention on the other hand, not only enables cule'r said i U r boiling fraction with an aluminum hexaaas generally unavoidably in admixture the invention has been directed to the production of cyclohcxane',1the invention is not'necessarily mama cracking at a temperature 600- C. and limited to the production oi only this cycle-- paraflin and may be applied with advantag to 'the production or other cycloparafllns of hydroaromatic structure 'irom complex naphthenic -hydrocarbonmixtures.--ifThus the process or the as dimethylcyclopentane and a fraction comprising cycloparamns of hydroaromatic structure having seven carbon atoms to the molecule such as methylcyclohexanc and the paraiiinic hydrocarbons oi' close boiling range inseparable therefrom by fractionation on a practical scale. The fraction comprising the cycloparamn oi nonhydroaromatic structure is passed to the iso merization zone 8 whereas the fraction comprising the cycloparamn of hydroaromatic structure in admixture with open chain paramns is passed to the selective paraflln cracking zone 26. Cycloparaflins of hydroaromatic structure of high purity are separated from the products oi theisomerization and selective cracking zones.

For the purpose of simplicity parts of apparatus 'such as pumps, separators-coolers, condensers and detailed showing of reactors, etc., not essential to a'complete understanding of the invention have been omitted from the drawing.

Similarly iractionating zones depicted in the drawing by single fractionators will in actual practice comprise the use of more than one fractionator to enect the indicated separations.

We claim as our invention:

1. Process for theproduction of cyclohexane from a hydrocarbon mixture comprising methylcyclopentane, cyclohexane and open chain paratiinshaving six and seven carbon atoms to the molecule, whichcomprises separating a lower boiling traction comprising-methylcyclopentane and a higher boiling fraction comprising cyclohexane, methyl cyclopen'tane and open chain paraillns having seven carbon atoms to the molesaid hydrocarbon mixture, contacting chloride'isomerization catalyst at methylcyclopentane isomerizing conditions in an isomerization zone, thereby converting methylcyclopentane to cyclohexane, subjecting said higher boiling fraction ,to thermal cracking at a temperathe recovery of substantially all oi' the available I methylcyclopentane and. cyclohexane in readily available naphthenic hydrocarbon mixtures, but

enables their recovery as a cyclohexane' ofa v parai'iins diflicult to separate therefrom by iractionating means. There is thus assured the passageof a minimum or material through the crackingzone facilitating not only selectivity in crackingbut avoiding the subjection of methylcyclopentane to the cracking conditions. It furthermore avoids the passage into the cracklng zone, and consequent conversion to less valuable materials, of desirable open chain ture of from about 550 C. to about 650 C. for a period of time from about 10 to about 20 seconds in a thermal cracking zone, thereby converting open chain parafllns to lower boiling hydrocarbons, fractionally distilling hydrocarbons comprising cyclohexane and hydrocarbons comprising .methylcyciope'ntane from the eiiluence or said isomerizaticn and said cracking zones, and recycling said hydrocarbons comprising methylcyclopentane to said isomerization zone. v

2. Process for the production of cyclohexane from a hydrocarbon mixture comprising methylcyclopentane, cyclohexane and open chain paraiiins having six and seven carbon atoms to the molecule, which comprises separating a lower boiling fraction comprising methylcyclopentane and a higher boiling traction comprising cyclohexane, methylcyclopentane and open chain parfrom said hydrocarbon mixture, contacting said lower boiling fraction with an aluminum halide auaoce amns having seven carbon atoms to the molecule" isomerization catalyst at methylcyclopentane.

lsomerizing conditions in an isomerization zone, thereby converting methylcyclopentane to cyclohexane, subjecting said higher boiling fraction to thermal cracking at a'temperature of from about 500- C. to about'lOO" C. for a period of time oi' from about to about 30 seconds in a thermal cracking zone, thereby converting open chain parafl'ins'to lower boiling hydrocarbons, fractions ally distilling hydrocarbons comprising cyclohexane and hydrocarbons comprising methylcyclo pentane from the eilluence oi said isomerization and said cracking zones, and recycllngsaid hydrocarbons comprising methylcyclopentane to said isomerization zone.

3. Process for the production'of cyclohexane from a hydrocarbon mixture comprising methyl cyclopentane, cyclohexane and open chainv parafllns having six and seven carbon atoms to the one from naphthenic gasoline, which comprises separating a lower boiling fraction comprising erization zone, thereby converting methylcyclopentane to cyclohexane, subjecting said higher boilingfraction to thermal cracking at a temperature of from about 550 C. to about 650' C. for

a period or timeoi from about 10 to about 20 seconds in a thermal cracking zone, thereby converting open' chain parafllns to lower boiling hy drocar-bons, fractionally distilling hydrocarbons comprising cyclohexane and hydrocarbons comprising methylcyclopentane irom the eilluence of said isomerization and said cracking zones, and

- recyclingsaid hydrocarbons comprising methylmolecule, which comprises separating a lower boiling fraction comprising methylcyclopentane and a higher boiling fraction comprising cyclohexane, methylcyolopentane and open chain par-,

cyclopentane to said isomerization zone.

6. The process for the production of cyclohexanei'rom naphthenic gasoline, which comprises separating a lower boiling fraction comprising afllns having seven carbon atoms to the molecule I from said hydrocarbon mixture, contacting said lower boiling fraction with an isomerization catalyst comprising a metal halide of the Friedel- Craits type at methylcyclopentane isomerizing conditions in an isomerization zone, thereby converting methylcyclopentane to cyclohexane, subiecting said higher boiling fraction to thermal selective paraffin cracking conditions at a temperature oi. from about 500 C. to about 700 C. for a period of from about 5 to about seconds in a thermal cracking zone, therebyconvertlng open chain paraflins to lower boiling hydrocarbons, fractionally distilling hydrocarbons comprising cyclohexane and hydrocarbons comprising methylcyclopentane from the efiluence of said methylcyclopentane having a maximum boiling point of about 75 C. and a higher boiling fraction comprising cyclohexane, methylcyclopentame and open chain parafllns having a maximum boiling range of about 85 C. from said gasoline, contacting said lower boiling fraction withan aluminum halide isomerization catalyst at methylcyclopentane isomerizing conditions in an isomerization zone, thereby converting methylcyclopentane .to cyclohexane; subjecting said higher boiling fraction to thermal cracking at a verting open chain paramns to lower boiling hytemperature of from about 500 C. to about 700 C. for a period or from about 5 to about 30 seconds in a thermal cracking zone, thereby con- ,drocarbons, fractionally distilling hydrocarbons isomerization and said cracking zones, and recycylng said hydrocarbons comprising methylcy clopentane to said isomerization zone. 4

.4. Process i'or-the production of cyclohexane from a 'naphthenlc gasoline traction having a maximum boiling point below the boiling point of normal heptane and comprising methylcyclopentane, cyclohexane and open chain parafllns having six and seven carbon atoms to the molecule, which comprises separating a lower boiling fraction comprising methylcyciopentane and a higher, boiling fraction comprising cyclohexane, methylcyclopentane and open chain parafflns having seven carbon atoms to the molecule from said hydrocarbon mixture, contacting said lower boiling traction with an aluminum halide isomerizatlon catalyst at methylcyclopentane isomv erizing conditions .in an isomerization zone,

' thereby converting methylcyclopentane to cyclohexane, subjecting said higher boiling fraction to selective paraflin cracking conditions at a temperature of from about 500 C. to about 700 C. for a period of-time of from about 5 to about 30 seconds in a thermal cracking zone, thereby converting open chain parafiins to lower boiling hydrocarbons, fractionally distillin hydrocarbons comprising cyclohexane and hydrocarbons comprising methylcyclopentane from the eiliuence of said isomerization and said cracking zones and recycling said hydrocarbons comprising methylcyclopentane to said isomerizatlon zone.

comprising cyclohexane and hydrocarbons comprising methylcyclopentane from the eilluence of said isomerization and said cracking zones, and

recycling said hydrocarbons comprising methylcyclopentane to said isomerization zone. i 'l. The process for the production of cyclohex- I one irom naphthenic gasoline, which comprises 5. The process for the production or cyclohexseparating a lower boiling fraction comprising I methylcyclopentane having a maximum boiling .point of about C. and a higher boiling traction comprising cyclohexane, methylcyclopentane and openchain paramns having a maximum boiling range of about C. from said gasoline, contacting said lower boiling fraction with an isomerizatlon catalyst comprising a metal halide oi the Friedel-Craits type at methylcyclopentane isomerizing conditions in an isomerization zone,

,thereby converting methylcyclopentane to cyclohexane, subjecting said higher boiling fraction to selective paratfln cracking conditions at a tem- Derature or from about 500C. to about 700 C. for a period or time of from about 5 to about 30 seconds in a thermal cracking zone. thereby converting open chain paraflins to lower boiling hydrocarbons, fractionally distilling hydrocarbons comprising cyclohexane and hydrocarbons comprising methylcyclopentane from the eflluence of said isomerization and said cracking zones, and recycling said hydrocarbons comprising methylcyclopentane to said isomerization zone.

4 WILLIAM E. ROSS.

PHILIP PEZZAGLIA. 

